[4] An adult Sacramento sucker representative coloration is a brown or black upperpart and yellow gold or white underpart.

[5] Other field marks include a conically slender head with a terminally located mouth and medium to large sized lips.

Anterior features include eyes located at the posterior half section of the head, and a minimal number of small gill rakers.

The sucker fish has the largest sized scales at its posterior half with a dorsal fin ranging from 0.50-0.53 millimeters in length.

Other key anatomical features consist of one possessing a straight lateral line, a homocercal caudal fin, and 12 to 13 rays.

[4] In 1973, John D. Hopkirk, ichthyologist and emeritus professor of Sonoma State wrote the species is an endemic fish to the Sacramento-San Joaquin province with several subspecies in the genus Catostomus.

Additional subspecies found in Clear Lake, Russian River, and Tomales Bay belong to Catostomus occidentalis.

More specifically, drainages of Sacramento-San Joaquin, streams and reservoirs of Oregon Goose Lake upper basin and upper Kern River drainage in San Joaquin and Tulare area as well as coastal spots such as Tomales Bay, and Mad, Bear, Eel, Navarro, Russian, Pajaro, and Salinas River.

[4] Suckers inhabit deep pools, undercut banks, or clear streams of river ecosystems from cold to warm temperatures (20-25 degree Celsius).

[4] The Sacramento sucker are strong swimmers overall using strategic sources for water flow and can be found in zones of channel margin or debris.

A 1998 study conducted by Christopher Myrick and Jospeh Cech, Jr. recorded the aerobic swim velocity of the sucker and other California stream fish.

[12] The fish only made subtle changes to critical holding velocity to manage experimental temperatures at a pace between 0.47-0.51 meters per second.

Overall, markers for altered genes are minimal or not present, so the contamination does not harm populations or the volume of pesticide in run-offs is negligible.

Due to the suckers spatial preference, staying close to the bottom substrate, makes contact virtually none with trout who occupy water column.

[15] Northern California bald eagles (Haliaeetus leucocephalus) prey on native and introduced freshwater fish species including Catostomus occidentalis.

Sacramento suckers provided an important part of the Achomawi's diet up until the 1950s and the remains of stone traps used to catch the fish in midwinter can still be found in the river.